German Published Patent Appln. No. 10 2009 055 117 describes a master brake cylinder for a hydraulic vehicle braking system and a method for operating same. The master brake cylinder has a rod piston, which may be referred to as a first piston, and a tubular second piston. The first piston is movable by the second piston by a predefined piston travel into a first pressure chamber of the master brake cylinder. The purpose of an entrainer device provided on the second piston is to cause the first piston to carry along the second piston after overcoming the predefined piston travel. The aim is for the first piston and the second piston to be able to act together on the first pressure chamber of the master brake cylinder after overcoming the predefined piston travel. In addition, the aim is for a floating piston to be able to act on a second pressure chamber of the master brake cylinder.